We currently use both spellings the british "behaviour" and the american
"behavior". However "behavior" is more used in the project so I think
it's worth dropping the british name.
Closes#6395
Since HTTPS is "the new normal", this update changes a lot of man page
examples to use https://example.com instead of the previous "http://..."
Closes#5969
Reported by the new script 'scripts/copyright.pl'. The script has a
regex whitelist for the files that don't need copyright headers.
Removed three (mostly usesless) README files from docs/
Closes#5141
